CMake find_package command with a specific version of CGAL is failing

[VincentRouvreau]

Issue Details

When I specify a minimal CGAL version to CMake find_package command, CGAL is not and I have the following warning:

CMake Warning at CMakeLists.txt:4 (find_package):
  Could not find a configuration file for package "CGAL" that is compatible
  with requested version "4.12.0".

  The following configuration files were considered but not accepted:

    ~/miniconda3/envs/gudhi-devel/lib/cmake/CGAL/CGALConfig.cmake, version: 5.5.2

And CGAL is not found.

I work in a conda environment, where I installed cgal-cpp package.

Source Code

cmake_minimum_required(VERSION 3.14)
project(cgal_find_package CXX)

find_package(CGAL 4.12.0)

if(TARGET CGAL::CGAL)
  message("CGAL target found")
endif()

if(CGAL_FOUND)
  message("CGAL found")
endif()

Environment

• Operating system (Windows/Mac/Linux, 32/64 bits): Ubuntu 22.04 64 bits
• Compiler: g++ (Ubuntu 11.4.0-1ubuntu1~22.04) 11.4.0
• Release or debug mode: Release
• Specific flags used (if any): cmake -DCMAKE_BUILD_TYPE=Release -DCMAKE_PREFIX_PATH=$CONDA_PREFIX ..
• CGAL version: 5.5.2
• Boost version: 1.78.0
• Other libraries versions if used (Eigen, TBB, etc.):

[mglisse]

CGALConfigVersion.cmake has this logic:

if(PACKAGE_VERSION VERSION_LESS PACKAGE_FIND_VERSION)
  set(PACKAGE_VERSION_COMPATIBLE FALSE)
else()
  if(PACKAGE_FIND_VERSION_MAJOR STREQUAL CGAL_MAJOR_VERSION)
    set(PACKAGE_VERSION_COMPATIBLE TRUE)
  else()
    set(PACKAGE_VERSION_COMPATIBLE FALSE)
  endif()
  if(PACKAGE_FIND_VERSION STREQUAL PACKAGE_VERSION)
    set(PACKAGE_VERSION_EXACT TRUE)
  endif()
endif()

i.e. to be compatible, the version of CGAL found must have the same major version as the one requested. I am not sure that makes sense for CGAL, there are small ABI breaks between the last 4.* and 5.0, but I don't think they were that much bigger than some that happened for minor releases.

[VincentRouvreau]

Ok, thanks @mglisse
This should workaround the issue:

find_package(CGAL 4.12.0)
if(NOT CGAL_FOUND)
  find_package(CGAL 5.0.0)
endif()